As more and more of my CloudFormation (CF) stacks use a base image and CloudFormation::Init magic, it’s become imperative to have an AMI that has the helper scripts (cfn-signal, cfn-init, etc.) built-in. This isn’t a problem if you use the Amazon Linux AMI, but if you’re playing with things like immutable infrastructure or baking your own custom AMIs for CIS hardening or some other regulatory requirement, it can become a big issue quickly. There’s a little documentation out there on installing the CF helper scripts (http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-helper-scripts-reference.html) but the installation process is not quite so straightforward as one would hope.

The solution to this issue varies depending on your OS. I’ve had no issue with Windows AMIs because the Ec2Config service takes care of everything, but in CentOS and RHEL, there are a few extra steps. I’ll break them down by OS. Note that you may need to search for updated version of things like epel-release to make sure it matches your OS or you’re using the most current version.

CentOS 6

This was relatively painless, thanks to the contents of the cloudformation-examples bucket being publicly visible. The latest version of the helper-scripts requires some Python elements/versions that are a pain to set up, but you can use an older version of the helper scripts without any issues. As of CentOS 6.8, you can (more…)